(1) Field of the Invention
This invention relates to a lens adjusting device, and more particularly relates to a lens adjusting device of a projector.
(2) Description of the Prior Art
FIG. 1 is a block diagram showing a conventional projector 10. As shown in FIG. 1, the projector 10 has a light source module 12, an image module 14, and a projection module 16. The light source module 12 provides light beams for projection. The image module 14 adopts the light beams from the lamp source module 12 to transfer an input image signal into an imaging light beam. The imaging light beam is projected to a screen through the lens of the projection module 16.
The position of images on the screen is adjusted to satisfy the need of observers. For this purpose, a conventional method is to dispose a lens adjusting device in the projector to adjust the location of lens. FIG. 2 is a schematic view of a conventional lens adjusting device 100 in a projector. As shown, the lens adjusting device 100 includes a base 120, a vertical adjusting frame 140, and a horizontal adjusting frame 160. Two guiding rods 130 are disposed by the left and the right sides of the base 120 respectively. The vertical adjusting frame 140 is assembled on the two guiding rods 130. In addition, two guiding rods 150 are disposed by the up and the down sides of the vertical adjusting frame 140 respectively. The horizontal adjusting frame 160 is assembled on the two guiding rods 150. The lens 180 is fixed on the horizontal frame 160. In the lens adjusting device 100, the vertical adjusting frame 140 may be regarded as a vertical movable platform and the horizontal adjusting frame 160 as a horizontal movable platform, so as to achieve the object of adjusting the position of the lens 180.
Noticeably, the lens adjusting device 100 needs two separated frames 140,160 and four guiding rods 130,150 to adjust the position of the lens 180. The whole structure is rather complicated. Excessive components raise not only cost but also weight of the entire device. In addition, a greater room is also needed for holding this lens adjusting device 100.
Furthermore, the lens adjusting device should be able to fix the lens 180 at the adjusted position. The vertical adjusting frame 140 and the horizontal adjusting frame 160 as shown in FIG. 1 lack the ability of fixing the lens. Since a motor (not shown) is usually capable of driving a gear group to adjust the vertical adjusting frame 140 and the horizontal adjusting frame 160, the lens 180 may be fixed by restricting the rotation of the motor. Thus, it creates extra burden for the motor in this way. Besides, if the position of the lens is adjusted manually, it is unable to use the motor to fix the position of the lens 180.